Comment by tzebco

Yep, that's the ideal approach for decent browsers. A curious caveat is that IE 8 and below will interpret that example HTML as <custom-ele></><stdelement></> (ie. as siblings, not parent and child) and therefore not apply any component-scoped styles. Not ideal.

Of course nobody uses those browsers anymore, the same caveat applies to non-custom HTML5 elements, and the bad behavior has long been preventable with JavaScript [0]. But anyone (else) with an extreme backwards compatibility mindset might consider if they could instead bootstrap from <div class="custom-ele"><stdelement></></> and (if needed and in window) a coordinating MutationObserver.

[0] https://web.archive.org/web/20091031083341/http://diveintoht...